Medical instruments and devices are routinely sterilized by a high-pressure vapor sterilization method using water vapor saturated under a high pressure or by an ethylene oxide gas sterilization method using a chemical material such as ethylene oxide that does not cause thermal damage to tools or materials susceptible to heat.
More specifically, a high-pressure vapor sterilizer or an autoclave performs sterilization at a high temperature of about 120° C. or higher and may thus shorten the life of medical instruments and devices by causing deformation of medical appliances formed of a synthetic resin and blunting the sharp edges of medical appliances formed of steel. Particularly, expensive medical instruments and devices that are on the increase due to recent developments in surgical technology are generally susceptible to heat or moisture and are highly likely to be damaged during sterilization reprocessing. Thus, the high-pressure vapor sterilization method may not be a suitable option for such expensive medical instruments and devices.
An ethylene oxide gas sterilizer capable of minimizing thermal damage to medical instruments or devices can perform sterilization at low temperature, but requires a ventilation time of more than 12 hours after sterilization because of the possibility of any remaining ethylene oxide gas or the reaction products thereof causing carcinogenic or toxic substances. Also, the use of an ethylene oxide gas requires great care because an ethylene oxide gas is highly explosive, has been reported to serve as a genetic toxic substance causing mutations, and has even been known as a carcinogenic substance.
A sterilization method using hydrogen peroxide vapor boasts of various advantages, for example, a short sterilization time of about 30 to 60 minutes at a temperature of 40 to 50° C. and the release of harmless sterilization by-products to the human body or the environment, such as water and oxygen, and can address the shortcomings of a high-pressure vapor sterilizer and an ethylene oxide gas sterilizer.
However, during the vaporization of a hydrogen peroxide solution, which is used to produce hydrogen peroxide vapor, water evaporates and diffuses faster than hydrogen peroxide, thereby interfering with a sufficient diffusion of hydrogen peroxide. More specifically, water has a higher vapor pressure than hydrogen peroxide and thus evaporates more quickly than hydrogen peroxide. Also, since water has a smaller molecular weight than hydrogen peroxide, water vapor diffuses more quickly than hydrogen peroxide vapor.
Due to the aforementioned properties of water and hydrogen peroxide, a high concentration of water arrives at a product to be sterilized faster than hydrogen peroxide when a hydrogen peroxide solution is vaporized in the space surrounding the product.
Water vapor diffuses into a diffusion restriction space, such as a small gap (or a crevice) or a long narrow lumen, thereby suppressing the transmission of hydrogen peroxide vapor. That is, since water arrives at the product ahead of hydrogen peroxide, the product may not be able to be properly sterilized.
For an effective sterilization, it is preferable to use a highly-concentrated hydrogen peroxide solution, but in reality, it is difficult to transport, store, and handle a hydrogen peroxide solution having a concentration of 60 wt % or higher.
However, even with such numerous benefits, the sterilization method using hydrogen peroxide vapor is more limited than a high-pressure vapor sterilization method and an ethylene oxide gas sterilization method by the shape of a target object to be sterilized due to weakened diffusability of hydrogen peroxide.
In the meantime, Korean Patent Application Publication No. 10-2006-0052161 relates to a sterilization system and method and an orifice inlet control apparatus therefor, and discloses a sterilization method in which a diffusion restriction is placed into a path of evacuation of a vaporizer so as to condense hydrogen peroxide vapor while passing water vapor and the hydrogen peroxide vapor is vaporized and diffused into a sterilization chamber.
However, in the sterilization system and method of Korean Patent Application No. 10-2006-0052161, once a hydrogen peroxide solution reaches a predetermined concentration or higher, the ratio of hydrogen peroxide vapor to water vapor vaporized from the hydrogen peroxide solution becomes uniform, or increases. As a result, the concentration of the hydrogen peroxide solution no longer increases, and instead, the total amount of the hydrogen peroxide solution decreases.
Also, due to a restriction imposed by the diffusion restriction on the movement of a fluid, a higher temperature is needed to vaporize hydrogen peroxide, leading to a greater loss of a high-concentration of hydrogen peroxide. Also, since the temperature of hydrogen peroxide vapor is high, the hydrogen peroxide arrives first at the packaging material of a target object to be sterilized or a chamber structure, which has a low temperature, and condenses, thereby interfering with a rapid vaporization and diffusion.